JOHANNESBURG — South African construction workers at stadiums being built for the 2010 World Cup went on an indefinite strike Wednesday in a move that could derail the tournament.

About 70,000 workers at stadiums across the country set down their tools after wage negotiations deadlocked earlier this week.

Workers are demanding a 13 percent pay increase while employers are only offering 10.4 percent.

The strike could delay the completion of flagship projects such as the Soccer City stadium in Johannesburg, the Green Point stadium in Cape Town and the Moses Mobhida stadium in Durban.

Stadiums need to be completed by December to meet FIFA deadlines before the tournament kicks off in June 2010.

Lesiba Seshoka, from the National Union of Mineworkers, which represents construction workers, said the strike would continue until employers met their demands.

The unions have complained that some workers are earning about $1.50 an hour and others $5 a week. Workers in South Africa are supposed to earn a minimum wage of about $200 a month.

"It is a very sad situation in which people think workers must be sacrificial lambs because there is a recession whilst that recession also affects our members more," Bhekani Ngcobo, a union negotiator said in a statement.

The workers have been criticized for jeopardizing South Africa's chances of hosting a successful World Cup.

But the Congress of South African Trade Unions, which represents the country's largest trade union federations, has come out in support of the construction workers and says the dispute is not targeted at the World Cup.

"COSATU, and the construction workers, are as passionate about the 2010 World Cup as anyone, and will do everything possible to ensure its success. But we will not tolerate the stadiums being built by workers who are underpaid or working in dangerous or unhealthy conditions," the organization said in a statement.

Danny Jordaan, chief executive of the local organizing committee, said the strike would soon be resolved and was confident that stadiums will be completed on schedule.

"The construction workers have been the lifeblood of the 2010 FIFA World Cup project. Their hard work has ensured that we are on track to meet our deadlines and that our stadiums will be among the best in the world next year," he said in a statement.

A spokesman from the employers body, the South African Federation of Civil Engineering Construction, was not immediately available for comment.

Patrick Geqeza, a shop steward for workers at the Soccer City stadium in Johannesburg, said he understood the importance of having the World Cup in South Africa and completing the stadiums in time.

"We feel bad about going on strike," he said, but added there was little alternative.

Associated Press Writer Stuart Moir contributed to this report.